North Korean leader Kim Jong-un visited a military unit near the tense inter-Korean border earlier this month when he was absent from public appearances for 15 days, Yonhap news agency quoted sources as saying Tuesday.

In early August, Kim made an inspection not covered by the state media at the front-line unit, some 1 kilometer away from South Korea's general outpost (GOP) in the central section of the border, the sources added.

It is not known what activity the North's leader made there, but South Korea's military is viewing the inspection as an unusual, undisclosed move, bracing for North Korea's possible tactical provocations, according to the sources.

The supervision was seen as being conducted sometime before August 14 when Kim inspected the command post of the Strategic Force. At that time, he delayed a plan to fire four missiles toward the US territory of Guam.

For 15 days, he had not shown up in public since July 30 when Kim attended a banquet celebrating the country's test of an intercontinental ballistic missile (ICBM) days earlier.

A military official said that the border unit inspected by Kim is surrounded by mountainous areas and streams, making it easier for the North Korean military to make surprise provocations.

South Korean and US troops kicked off 10-day joint military drills Monday, which Pyongyang has denounced as a rehearsal for a northern invasion.

Source: MENA